This invention relates to containers and, more particularly, it relates to containers constructed of relatively low strength materials which are well-suited for packaging products requiring increased structural integrity and a hermetic seal, such as food and/or pressure-producing products.
It is very desirable to have an inexpensive container suitable for packaging various food items and pressure-producing products, such as carbonated beverages and beer. However, suitable containers for such products have been rather expensive due to the high strength characteristics necessary to maintain the hermetic seal.
In recent years, there have been introduced a number of different types of lightweight, composite containers constructed of low strength materials which are considerably less expensive than the commonly-used tin plate and aluminum containers. Such inexpensive containers normally are comprised of a cylindrical composite can body closed at both ends by metal caps which are attached to the body by a standard double-seaming method. In this standard double-seaming method, a curved extension of the metal end is folded over together with a flange portion on the fiber can body so as to form a double-seam joint. Such standard fiber containers have experienced difficulty in packaging certain food items and certain pressure-producing products because the joint between the metal ends and the fiber body has not exhibited sufficient strength to maintain a hermetic seal and to withstand the pressure of the products container therein. Thus, end seam failure was frequently experienced when attempts were made to use standard double-seamed fiber cans for packaging pressure-producing products. Thus, even though standard fiber containers are much lighter in weight and less expensive than the stronger metal containers, they have not been suitable for use in packaging certain food items and some pressure-producing products.
An improved hermetically sealed composite container was provided in my U.S. Pat. No. 3,580,464 which issued on May 25, 1971. The improved composite container disclosed in this patent features the use of a compound material on the metal ends which, when heated, will form a bond with a thermoplastic material incorporated into the inner liner of the composite can body. Thus, this configuration provided both a mechanical double-seamed joint and a chemical-type bond which aided in providing a hermetic seal and withstanding the increased pressure of pressure-producing products. However, it has been found that while the configuration of my U.S. Pat. No. 3,580,464 was a considerable improvement over the existing prior art composite containers, it does not provide the necessary structural integrity required for packaging and shipping certain food items and other pressure-producing products. It has been found that during shipping certain impacts to the side area of the double-seamed end configuration could result in a reduction of the hermetic seal and loss of pressure from within the container.
Thus, there is a continuing need for, and it is an object of this invention to provide, an inexpensive container which provides improved strength to maintain a hermetic seal for successful packaging of food items and pressure-producing products.
Other objects, features and advantages of this invention will become obvious to those skilled in the art upon reference to the following detailed description and the drawings illustrating a preferred embodiment thereof.